Information on SIMS Channel Plate ID's

The channel plate ID value serves as a measure to distinguish between different analyses over the three-year period. The channel plate is the main image detector of the SIMS mass spectrometer. Its performance directly affects instrument performance and output. Degradation and damage during use change the channel plate response in an unpredictable way. To compensate for this effect, semi-quantitative abundance statements are based on signal intensities ratioed to a certain element (Mg in these analyses).

Three different sets of channel plates were used:

Set number 2 was damaged at or before 4-22-93 probably due to unsuitable channel plate gain values. An example of a probably damaged set of channel plates is shown below.

This image was combined from PC IDE datafile editor screens.

Note the asymmetric aluminum signal of the MOS detector's surface. Aluminum being the dominating signal of the MOS detector's surface, this signal should, in theory, be perfectly symmetric with exception to the almost circular shaped discharge. Channel plate asymmetries are not recorded per default in the database. Be aware of this when making any assumptions on spots being visible in one corner or side of an impact feature. Always check the Al, Si, Si2 and Ca signals for asymmetries when looking at MOS samples and the respective substrate images for other samples.

Klaus G. Paul, 6-15-1994